French patent FR-2,842,435 describes a device for mixing and distributing a liquid fluid and a gaseous fluid, arranged upstream from a granular bed in a reactor. The device described in this patent comprises a plate equipped with risers, said risers being fitted with an upper part opening above the plate and with a lower end communicating with the underside of the plate, the upper part of the risers being provided with lateral orifices. In this device, the liquid is carried by a tubular system from outside the reactor to the distribution plate, so that the lower end of said tubular system remains immersed in the liquid accumulated above the plate.
The drawback of such a system is that the gas and the liquid are brought separately into the reactor. In fact, it is often desirable to maximize contact between the gaseous fluid and the liquid fluid prior to distributing the mixture consisting of these fluids homogeneously over the entire section of the reactor. It is often important, notably in the case of chemical processes, for the liquid feed to be saturated with reactive compounds from the gaseous fluid, even before the mixture of gas and of liquid flows through the catalytic bed.
An additional drawback of such a system is that it can be charged only with a significant amount of liquid to fill the tubular system. The liquid velocities are therefore high at the lower end of the tubular system or at the orifices of the tubes forming the continuation of this end. This may be a source of disturbance of the interface between the gas and the liquid, which compromises the homogeneity of the mixture of gas and liquid, on the one hand, and the uniformity of the distribution of such a mixture at the upper surface of the bed, on the other hand.
International patent application WO-95/35,159 describes a distribution system for driving a gas and a liquid through the surface of a fixed bed of solids comprising a distribution plate and a plurality of tubes extending through said plate, each one of said tubes being provided with a plurality of lateral orifices extending vertically above the upper face of the plate, wherein two groups of these tubes are noticeable by the vertical position of their lateral orifices. The device described in this patent application allows, thanks to the position of the lateral orifices of the two groups of tubes, to reduce the flow of liquid flowing through the plate when the height of liquid accumulated on said plate reaches a level below which one of the group of tubes comprises no lateral orifice. Furthermore, the gas and the liquid are carried to the distribution plate by means of vertical tubes mounted on the upper face of said plate and of slots provided at the base of these tubes.
The drawback of such a system is that the gas and the liquid are fed as a mixture onto the upper face of the distribution plate. This introduction mode generates, partly because of the gas bubbling in the liquid, disturbances at the interface between the gas and the liquid.
The device according to the present invention allows to reduce or even to overcome the aforementioned drawbacks.